Why don’t we use para-aminobenzoic acid (PABA)?

If it is possible to use 4-aminobenzoic acid as is to protect the skin from UVB rays, it is usually esterified into Padimate O, another UV filter. It is more stable and offers better formulation compatibility. Regulatory texts list para-aminobenzoic acid in Annex IV of Regulation (EC) No 1223/2009. This annex covers the UV filters permitted in the European Union. PABA may also be used in the United States, at a maximum concentration of 15%, compared with 5% in Europe.

4-Aminobenzoic acid is less used in skincare because its toxicological profile raises concerns for the skin. That is why we exclude this UV filter from our formulations. Para-aminobenzoic acid is linked to allergic and photoallergic reactions. Several clinical studies have shown its capacity to cause these reactions in people with photodermatosis.

At a Norwegian dermatology clinic, 23 patients with redness or burning sensation after sun exposure were examined. 48% tested positive in skin tests for PABA, either by direct contact or after UV irradiation. In a larger study by a Scandinavian research group involving 1,993 patients suspected of photodermatoses, 44 allergic reactions to para-aminobenzoic acid were reported, a reaction rate of 2.2%. These data suggest that this sunscreen filter may be a significant sensitising agent, in sensitive or photosensitive skin types.

Moreover, PABA appears to be capable of penetrating the skin barrier. This is suggested by several studies in vitro and in vivo. In an experiment on human volunteers, about 11.5% ± 6.3% of the applied PABA was recovered in the urine after 24 hours, indicating significant systemic absorption. In this study, the formulation was applied to the forearm of healthy subjects without occlusion and rinsed off after 24 hours. Despite this delayed removal, a significant proportion of the molecule had entered the body.

Note : Based on a review of the scientific literature by the Scientific Committee on Consumer Safety, an independent scientific committee managed by the European Commission’s Directorate-General for Health and Consumers, PABA does not pose mutagenic, carcinogenic, or teratogenic risks.

Does para-aminobenzoic acid pose environmental concerns?

The potential environmental effects of 4-aminobenzoic acid have been little studied. Based on available data, this UV filter does not appear persistent but it may be toxic to aquatic organisms. For example, the median lethal concentration (LC50) after 48 hours in aquatic invertebrates is approximately 10.03 mg/L. At this concentration half of exposed fish do not survive the period. For fish, 96-hour exposure reveals an LC50 of about 1.041 mg/L, indicating greater toxicity to these organisms.

These data from the ECHA database (European Chemicals Agency) show that the environmental impact of para-aminobenzoic acid cannot be ignored.